Sonnenberg, Mountain summit in Lucerne, Switzerland.

Sonnenberg is a mountain summit near Lucerne that rises to around 800 meters and offers views across Lake Lucerne and the surrounding Alpine peaks. The slopes show a mix of natural forest and farmed terraces crossed by several walking routes.

Coal was discovered on the Sonnenberg in the 1830s, and commercial mining began in March 1839. Output rose during both world wars: in World War I the firm Gustav Weinmann drove numerous tunnels and mined almost 8,000 tonnes with 40–50 miners in 10-hour shifts, while in World War II the Fuga AG produced over 20,000 tonnes for regional industry. The former Sonnenberg civil defence shelter, one of the world's largest, lies under the eastern part of the mountain.

The Sonnenbergbahn funicular opened in Kriens in 1902 and, as of 2011, still ran in its original condition, though not all year round. The mountain's name appears in the Chrüzhöchi meadow knoll at 775.7 m, the highest trigonometric point. Visitors also pass reservoirs holding spring water from the Pilatus region for Lucerne's drinking supply.

From downtown Lucerne, a walk of about one hour through the forest leads to the summit, with yellow markings showing the way through the Gütsch woodland. The route is easily accessible on foot, and there are rest spots and places to eat along the way.

The Sonnenbergtunnel carries the A2 motorway beneath the eastern part of the hill, through the Gigeliwald and Gütschwald woods. In the same area lies the former Sonnenberg civil defence shelter, described in the sources as one of the largest such installations in the world.